Patent GB-190322911-A (GB)
Title: Improvements in Alternating Current Motors.
Inventor: CAROLAN EDGAR ALFRED
Filed: 1903-10-22
Granted: 1904-10-22
Abstract: 22,911. Carolan, E. A., [General Electric Co.]. Oct. 22. Motors, controlling.-An alternating-current motor is arranged so that, when starting, it operates as an induction motor until synchronism is attained, and then automatically operates as a synchronous motor. The conditions when synchronism is attained are improved by a further movement of the controlling-switch. The motor is provided with a sectional primary winding fed with three-phase current and adapted to be arranged in y when starting the motor, and in A when synchronism is attained. Its secondary is provided with two or more windings, each adapted to be closed through variable resistances, one or more of them being also fed with direct current and having more copper in it or them than the others. Fig. 1 shows such a motor with its controlling-switch. The primary P is shown with windings of the Gramme type, but the drum type is preferable. The primary winding comprises six sections, each of which is in this case subdivided into two smaller sections x<1> to x<4>, y<1> to y<4>, w<1> to w<4>, the ends of which are connected to the fixed contacts 2 to 5, 7 to 10, and 12 to 15, of the controller C. The secondary S has two windings f, g displaced 90‹ from each other, and connected respectively between collecting-rings h, i and i, k. Brushes l, m, n connect these rings to fixed contacts 17 to 24. The ring i is also connected to the meeting point of two sections r<1>, r<2> of a resistance R, arranged as shown. The fixed contacts 1, 6, and 12 are connected to the mains a, b, c of a three-phase system, and the contacts 16, 25 are connected to direct-current mains e, d. Movable contacts Z<1> to Z<18> are provided on the controlling- cylinder as shown. In the position 1 of the cylinder, the coils x<1> to x<4>, y<1> to y<4>, and w<1> to w<4> are connected in three series, and the series are arranged in y between the mains a, b, c. The winding f, which contains more copper than the winding g, is closed through the resistance r', and is also connected across the mains d, e. The winding g is closed through the resistance r'. The motor now acts as an induction motor. In the position 2 of the cylinder, portions of the resistances r<1>, r<2> are cut out, and, in the position 3, all of the resistance r' and most of the resistance r<1> are cut out. In this position, the motor will run synchronously, the winding g acting merely as a damper to prevent hunting. On turning the controller to the position 4, the series of coils x<1> to x<4>, y<1> to y<4>, and w<1> to w<4> are arranged in #, and in addition the pairs x<1> x<4>, y<1> y<4>, w<1> w<4> are arranged in parallel respectively with the pairs x<2> x<3>, y<2> y<3>, w<2> w<3>, so that the voltage through each coil is increased largely. The resistance r<1> is disconnected, the motor now acting entirely as a synchronous motor. Either the gamma or # formation may be used throughout. Several coils g may be provided, the angle of displacement on the secondary S being altered to correspond. The coils f, g may be similar, direct current being then supplied to all of them.